1. Field of the Invention
The present invention relates to a planar light emitting element such as a backlight to be used in a liquid crystal display device or the like, an image display element, and an image display device using the planar light emitting device and the image display element.
2. Description of the Related Art
JP-A-2005-62741 (Patent Document 1) discloses a display device having an illumination device, a plurality of picture elements, and a plurality of light focusing elements. The illumination device is adapted to emit light toward the light focusing elements from a front side thereof. The picture elements are juxtaposed to each other. Each of the picture elements has a transmission region for transmitting light incident on the picture element from the illumination device. The light focusing elements are provided for the respective transmission regions and on the front side of the illumination device. Spots of light fluxes transmitted through the respective light focusing elements are formed on a plane defined by the respective picture elements and in the respective transmission regions of the picture elements to ensure that the centers of the spots are located in the respective transmission regions. The position (in a column direction) of the center of a light spot formed on one of the picture elements is different from the position (in a column direction) of the center of a light spot formed on a picture element adjacent to the one of the picture elements in a row direction.
JP-A-2005-268201 (Patent Document 2) discloses a planar light source device having a light guide plate and a concave deflection pattern formed on a lower surface of the light guide plate. The concave deflection pattern includes a light reflection portion, a flat portion and a directivity change portion. The light reflection portion faces the side of a light source and inclined with respect to the flat portion. The directivity change portion is located between the light reflection portion and the flat portion and adapted to increase the directivity of light to be incident on the light reflection portion. The planar light source device is capable of improving the directivity of light output from the light guide plate.
JP-A-H08-221013 (Patent Document 3) discloses a backlight device having a first light guide plate, a line light source and a second light guide plate. The first light guide plate has a refractive index n1. The surface of the first light guide plate is parallel to the surface of a liquid crystal panel. The line light source is provided on a side surface of the first light guide plate. The second light guide plate is provided on the first light guide plate and on the side of the liquid crystal panel with respect to the first light guide plate. The second light guide plate has a refractive index substantially equal to the refractive index n1. The second light guide plate has a collimation pattern formed on its surface facing the surface of the first light guide plate. The collimation pattern is formed to direct, toward the liquid crystal panel, light emitted by the line light source and repeatedly totally reflected.
JP-A-2001-312915 (Patent Document 4) discloses a planar light emitting element having a light source, a light guide member and an output light control plate. Light emitted by the light source is incident on both side surfaces (facing each other) of the light guide member. The output light control plate is provided above a light output surface of the light guide member. The output light control plate has a plurality of protrusions formed on a surface thereof facing the light output surface of the light guide member. The protrusions of the output light control plate are adapted to direct light output from the light output surface of the light guide member toward a direction substantially parallel to a normal to the light output surface of the light guide member. At least one optically transparent layer is provided between the light guide member and the output light control plate. Tip portions of the protrusions of the output light control plate are in contact with the at least one optically transparent layer. The protrusions of the output light control plate have respective refractive indexes higher than a refractive index of the light guide member. The at least one optically transparent layer has a refractive index higher than that of the light guide member.
JP-A-H09-113730 (Patent Document 5) discloses a planar light source device having a light guide plate and a linear light source provided on an incident surface of the light guide plate. The light guide plate has a light focusing pattern formed on a surface thereof and a deflection pattern formed on another surface thereof facing the surface on which the light focusing pattern is formed. The light focusing pattern has a relatively large average inclination angle (an average inclination angle is defined in Patent Document 5). The deflection pattern has a relatively small average inclination angle. Light emitted by the linear light source is repeatedly reflected within the light guide plate and output in a direction inclined at a small elevation angle with respect to a light output surface of the light guide plate and substantially parallel to the light output surface of the light guide plate. The output light is focused by the light focusing pattern and directed to a single direction. The planar light source device therefore has high directivity.
Non-Patent Document 1 (Applied Optics, Vol. 43, No. 24, pp. 4672-4676, 2004) discloses a planar light source in which output light has a polarization property by use of a material having a refractive index anisotropy.